Current computing devices may use head-mounted displays for virtual reality experiences. Compelling virtual reality experiences may require a relatively high pixel density (resolution) with a wide field of view and a fast refresh rate. Typical head-mounted displays include one or more display screens that are magnified for view by the user with a single-element lens, such as an aspherical lens or Fresnel lens. To achieve a wide field of view (greater than about 100 degrees), typical head-mounted display solutions require a display screen of greater than about 2.9 inches across.
Pancake lenses are folded optical systems, typically including two or more lens elements that use light polarization control to bounce light between the lens elements multiple times. Pancake lenses may achieve a high numeric aperture with a relatively short focal length. Pancake lenses may have relatively poor optical efficiency due to polarization losses. For example, typical optical efficiency for a pancake lens system may be less than 20%.